1. Field of the Invention
This invention relates to an articulated robot and more particularly to a retaining structure for a screw fastening unit in an articulated robot to be used for loading, unloading and assembling parts in small amounts.
2. Prior Art
These types of articulated robots are becoming more popular in many industrial fields and are utilized in wide applications because of their versatility. Since the robots are used in many applications, various kinds of robots have been developed, one kind of which being especially an articulated robot provided with two horizontal arms. It appears to be more suited for working with a plurality of work stations around it because of the smaller space required for its installation and its larger working area. That is why articulated robots have been utilized in various kinds of jobs. Consequently, it is desired that the robot can be easily adjusted without changing the height of the arm in response to the various kinds of workpieces needed so as to improve its versatility. This desire causes this type of robot to be improved.
Referring to the prior art shown in FIG. 4, an articulated robot includes a primary horizontal arm 2 and a secondary-horizontal arm 3 which respectively make pivotal motions by being controlled by a primary motor 11 and a second motor 22, respectively. The secondary arm 3 has a vertical through hole 46 wherein a vertical rod 26 having at the end a screw fastening unit is inserted and secured with two lockbolts 48 which secure the position. The robot 1 can be adjusted in a position suited for workpieces which are replaced on a work station after the bolts 48 are released and the rod 26 is slid down vertically along the through hole 46 in the secondary arm 3. After the rod 26 is positioned at a desired height, it is secured by the bolts 48 and the screw fastening unit can be fixed to the secondary arm 3 so that it can be used for various work pieces.
In the above prior art, the operator must hold a screw fastening unit 25 when the lockbolts 48 are released in order to slide it up and down with the rod 26 to a certain position. Then, the rod 26 is secured to the secondary arm 3 by screwing the bolts 48. This is, however, an annoying and difficult job to perform. Besides, if the operator is careless the screw fastening unit 25 sometimes falls down and hits a workpiece or the secondary arm 3, resulting in either the fastening unit 25 or the secondary arm 3 being damaged. It also would cause the rod 26 to turn by itself in the through hole 46 because of its inertia forces created when the secondary arm 3 swings at higher speeds and stops at a certain position.